1. Field of the Invention
An aspect of the present invention relates to an input module of a PLC, and more specifically, to an input module of a PLC, which receives a signal inputted from a sensor or switch.
2. Description of the Related Art
A programmable logic controller (PLC) applied to various fields such as automation of factory facilities in industries includes a central processing unit (CPU) module including a CPU, an input module that receives a signal inputted from a sensor or switch, a high-speed counter module that receives a signal inputted from an encoder, an output module that transfers a control signal to a motor or valve as a control object, a communication module, a proportional integral differential (PID) control module, a positioning module, and the like.
The high-speed module is a module that receives a signal inputted from a high-speed encoder so as to perform calculation using a microprocessor.
However, since the number of timer pulse units or interrupt modules of the microprocessor is limited, the high-speed counter module has a problem that it is difficult to configure multiple channels.
The high-speed counter module also has a problem that a separate module for processing a counter function is required to increase the number of channels.
In order to solve such problems, it is intended to perform the counter function using the input module, but the input module is implemented in such a manner to simply periodically read values. Hence, it is impossible to detect a rising or falling edge of a pulse.
Further, there is a limitation in increasing the number of channels.